If you don't use a mobile phone or Yandex doesn't send SMS's to your service provider, you can change your password using an alternate email address or by answering the security question.

What should I do if I got a message about my phone number being added, changed, or deleted?

If you are trying to do something with your main telephone number, just continue doing so: Yandex sends email and SMS notifications about all operations for security reasons.

If you got a notification unexpectedly, this means that someone got access to your account. Don't worry: you can easily restore access to your account using your main phone number. Without access to your phone, the hacker cannot delete or change the associated phone number for 30 days. During this time, you can: